Swivel

ABSTRACT

A washpipe assembly for use in drilling swivels wherein the assembly includes a washpipe, a sleeve for mounting the washpipe to the swivel body, and packing for sealing the space between the sleeve and washpipe. The packing comprises a plastic ring and a metal anti-extrusion ring mounted in a recess formed in the plastic ring.

[ 1 May 29, 1973 United States Patent [191 Heilhecker et a1.

[ SWIVEL 5/1944 Jackman...... 1/1972 Wahlmark 7/1958 [75] Inventors: JoeK. Heilhecker, Bellaire; William C. Maul-er; Everett H. Lock, both ofHouston, all of Tex.

....277/l88 X ...277/188 X Hayman 2/1946 Phillips 9/1956 Murphymm.3/1961 [73] Assignee: Esso Production Research Company,

Houston, Tex.

Oppenheim 9/1963 Dunn............... 10/1956 Josephson................

.[22] Filed: Aug. 23, 1971 n 0 S M v a D B msn hh 1O J C RV 4M e mR 0 e4A r .3 m a M y We m m0 P A 7 9 3 7 l 0 N L D. D. A 2 .1

Robert L. Graham et a1.

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References Cited packing for sealing the space between the sle washpipe.The packing comprises a eve and plastic ring and a extrusion ringmounted in a recess formed metal antiin the plastic ring.

UNITED STATES PATENTS 7 Claims, 3 Drawing Figures 2,676,788 4/1954Davidson et al. .................285/275 X Patented May 29, 1973 2Sheets-Sheet 1 JOE K. HEILHECKER WILLIAM C MAURER EVERETT H. LOCKINVENTORS HG.I

ATTORNEY Patented May 29, 1973 2 Sheets-Sheet 2 JOE K HEILHECKER WILLIAMC. MAURER EVERETT H. LOCK INVENTORS BY M% ATTORNEY SWIVEL BACKGROUND OFTHE INVENTION 1. Field of the Invention:

This invention relates generally to swivels. In one aspect, it relatesto an improved washpipe assembly usable in drilling swivels.

2. Description'of the Prior Art:

In oilfield drilling operations which employ rotary drilling techniques,drilling fluid is circulated through the drill string and up theborehole returning to the system pit or tanks. The drilling fluids serveseveral important functions such as cooling the bit, carrying thecuttings away from the bit, plastering the borehole wall to preventsluffing or caving of formations, and providing a hydrostatic head forcontrolling the influx of formation fluids. The swivel which is anessential component in all rotary drilling systems functionsto rotatablysupport the drill string and to deliver drilling fluid to the rotatingdrill string. The swivel normally contains a stationary support housingsuspended on the drilling rig hoisting equipment and a rotating stemfrom whichis suspended the drill string. Drilling fluid is delivered toa flow course formed in the swivel housing by means of a drilling hose.A tube, referred to as a washpipe, interconnects the flow course of thestationary housing and the interior of the rotating stem and thus servesto conduct fluid from the stationary portion to the rotating portion ofthe swivel. Packing rings positioned about the outer periphery of thewashpipe and maintained in place by a mounting sleeve provides a dynamicseal between the relatively rotating members and prevents the leakage offluid. The packing rings normally are composed of composite materials orflber reinforced elastomer. The washpipe, packing and mounting sleevesnormally are assembled as a unit to permit rapid replacement whenpacking rings become worn.

When operated at conventional drilling pressures, e.g. pump pressuresbelow about 2,500 psi, the swivel described above performssatisfactorily, requiring only occasional replacement of the washpipeassembly. The recent trend in high pressure drilling, however, hasnecessitated changes in the design of conventional fluid handlingequipment. For most system components, these changes have resultedmerely in the use of higher quality materials and/or increases in wellthickness of the pressurized components. A variety of high pressurestatic seals are available for coupling stationary components. Theswivel, however, must provide a dynamic seal between the relativelyrotating :members. High pressure tests have shown that the dynamic sealsconventionally used in washpipe assemblies fail within a relativelyshort period of time-usually less than one hour. It is thus seen thatthe use'of conventional washpipe assemblies in high pressure drillingwould result in frequent and time consuming shutdowns.

SUMMARY OF THE INVENTION I The improved swivel of the present inventionis capable of operating at high pressures for long periods of time. Anovel feature of the invention relates to an improved washpipe packingassembly employed in the swivel. Briefly, the packing assembly comprisesa plastic ring and a metal anti-extrusion ring. One end of the plasticring is provided witha recess configurated for receiving theanti-extrusion ring in close conformity. The plastic ring containing theanti-extrusion ring is maintained in sealing relation about the swivelwashpipe by means of a mounting sleeve. In the assembled condition, theanti-extrusion ring bears against an end wall of the mounting sleeve andagainst the outer periphe ry of the washpipe covering the mountingsleeve and against the outer periphery of the washpipe covering the gaptherebetween. The plastic ring surrounding the outer periphery of theanti-extrusion ring and bearing against'a top surface thereof servesseveral important functions: it provides a backup structure for theanti-extrusion ring preventing it from seizing to the mounting sleeve;it provides a radial component of force on the anti-extrusion ringforcing it into engagement with the washpipe; and it provideslubrication for the sliding surfaces of the assembly.

The plastic ring preferably is composed on a homogeneous plastic havinga relatively low coefficient of friction. The fluoroplastics,particularly polytetrafluoro- BRIEFDESCRIPTION OF THE DRAWINGS FIG. 1 isan elevational view of a drilling swivel with portions cut away toillustrate details of the washpipe assembly.

FIG. 2 isan enlarged sectional view of the washpipe assembly shown inFIG. 1.

FIG. 3 is an exploded perspective view of the sealing rings employed inthe washpipe assembly shown in FIG.

- DESCRIPTION OFTHE PREFERRED EMBODIMENTS The present invention will bedescribed in connection with a rotary drilling swivel, but it should beunderstood that the invention can also be applied in other types ofswivels where it is desired to couple two relatively rotatable, fluidconducting members in a fluid tight assembly.

As shown in FIG. 1, the main components of a swivel include an outerstationary body 10 having a flow course 11 formed therein, a tubularstem 12 journaled to'the body 10, a washpipe assembly 13 forinterconnecting the flow course 11 and the interior of the stem 12, anda bail 14 for suspending the swivel on the drilling rig hoistingequipment.

The swivel body 10 is normally fabricated from three steel castings: alower main housing 15, a housing cap or bonnet l6, and a fluid inletconnecting member 17. The parts l5, l6, and 17 are normally madeseparately and assembled as a unit by bolts or other fasteners. Thefluid inlet connecting member 17, referred to in the art as agooseneck", defines the flow course 11 i and is provided with a threadedouter end 18 for at- The stem 12 extends through the main housing 15 andhas an upper threaded end projecting above ;a closure plate 21 of cap16. The stem 12 extends downwardly through the lower end of housing 15terminating in threaded end 22. The kelley joint and the remainder ofthe drill string are suspended from end 22.

A flange 23 secured to the stem 12 is journaled to an internal shoulder24 of housing 15 by means of a thrust bearing 25. Upper and lower radialbearings 26 and 27 maintain the stem 12 in proper axial alignment withinhousing 15. The housing 15 is normally filled with oil to providelubrication for bearings 25, 26, and 27.

The swivel thus comprises two relatively rotatable, fluid conductingmembers which must be coupled together in a fluid tight assembly. Thisis the function of the washpipe assembly 13.

The washpipe assembly 13 interconnects the downwardly extendingprojection 19 of member 17 and the upwardly projecting end 20 of stem12. This assembly includes a washpipe 28, mounting sleeves 29 and 30 forconnecting the tube to the swivel, and packing assemblies 31 and 32 forsealing the space between the sleeves and the washpipe. The washpipe 28is a short, hardened steel tube smoothly ground to minimize packingwear. In many conventional swivels, the washpipe 28 is fixed to theconnecting member 17 and remains stationary therewith. This type ofconnection requires a static seal at the joint. In the preferredembodiment of the present invention, however, the washpipe 28 isprovided with a dynamic seal at both ends of the washpipe 28 so that thewashpipe 28 can remain stationary with the connecting member 17 or canrotate with the stem 12 depending upon the drag forces imposed thereon.In order to facilitate replacement of the packing assemblies, thewashpipe assembly 13 is normally constructed as a unit such that whenleakage occurs, the worn unit can be withdrawn and a new one installed.

In describing this preferred embodiment, it will be assumed that thedrag forces on the washpipe 28 are such that it rotates with the stem12. Thus the packing 32 in the lower sleeve 30 acts as a static seal andthe packing 31 in the upper sleeve 29 acts as a dynamic seal. Becausewear is more pronounced between moving parts, the dynamic seal tends tofail first in the washpipe assembly 13. This is particularly true whenoperating at extremely high pressures and when the drilling fluidcontains abrasives that tend to cut or abrade the packing materials.

Referring to FIG. 2, the sleeve 29 has a cylindrical section 33 arrangedin axial abutting relation with the projection 19 and an end wall 34. Anopening through end wall 34 is sized in relation to the outside diameterof washpipe 28 to permit free relative rotation between the washpipe 28and sleeve 29. The clearance between these two members normally will bebetween about 10 and 30 mils. A packing nut 36 threadedly con- Thesleeve 29 in combination with the washpipe 28 defines an annular space37 closed at one end by the end wall 34 and open at the other end influid communication with the interior of washpipe 28. The packingassembly 31 functions to seal the gap between the washpipe 28 and endwall 34 and comprises a series of stacked rings sized to fit into theannular space 37. The rings include a plastic ring 38 and a metalantiextrusion ring 39.

' As shown in FIG. 3, the plastic ring 38 is a cylindrically shapedmember having an axially extending recess 40 formed in one end thereof.The outside and inside diameters of the plastic ring 38 are sized to fitin close conformity with the cylindrical walls defining annular space37. The recess 40 is shaped to receive the metal anti-extrusion ring 39.The axial dimension of the recess 40 is about'the same as that of thering 39 so that their end surfaces lie about flush with each other asshown in FIG. 2. The inside diameter of the recess 40 can be about thesame as the outside diameter of the ring 39. The skirt portion of theplastic ring surrounding the outer periphery of the metal ring 39 shouldbe sufficiently thick to provide peripheral backing for the metal ring39. Thicknesses between about H16 and A inch are satisfactory for mostapplications. The radial dimensions of the plastic ring and metal ringare sized to permit the rings in assembled condition to slide throughthe annular space 37 and seat on end wall 34. Clearances of about 2 to10 mils between the rings and confining cylindrical walls aresatisfactory. When inserted in the space 37, the metal ring covers thegap between the wall 34 and washpipe 28 thereby preventing the extrusionof the plastic material as pressure is applied to the assembly. Theplastic ring 38 can be molded or machined from any one of the syntheticor natural resins normally used in bearing service. These plasticsinclude nylon, acetal and polycarbonate resins, fluoroplastics and thelike. The fluoroplastics, particularly polytetrafluoroethylene, arepreferred, however, because of their anti-stick properties, lowcoefficient of friction, and high temperature resistance. All of theseproperties are important in the functioning of the pack ing assembly.

The anti-extrusion ring 39 is circumferentially continuous andpreferably is machined from a relatively soft bearing metal (Brinnelhardness less than about l00) such as bronze, bronze alloy, copperalloy, and the like. The low modulus of elasticity of these metalsprovide good conformability and embedability at the rubbing surface.Phosphor bronze (SAE 660) has performed particularly well in the packingassembly.

The packing assembly can also include conventional self-sealing ringsshown as 41 in FIG. 2. These rings can be made of composite material orelastomers containing fibers of cotton, rayon, flax, jute, hemp, wool,and the like.

The packing is mounted by inserting the plastic ring 38 containing themetal anti-extrusion ring 39 in recess 40 through the annular space 37until the metal ring 39 engages the end wall 34. A plurality-usually37of the conventional self-sealing rings 41, if used, can then beinserted into the annular space 37. The first of these rings engages theplastic ring 38 and can be provided with a flat surface for distributingthe load thereon. The lower packing assembly 32 can be identical to theupper packing assembly 31 including plastic ring 42, anti-extrusion ring43 and self-sealing conventional rings 44. The sleeve 30 is secured tothe upper end 20 of stem 12 by packing nut 45. A washer 46 clampedbetween the sleeve 30 and stem end 20 maintains the washpipe 28 inproper position.

Under operating conditions, the plastic ring 38 surrounding theanti-extrusion ring 39 serves three important functions: 1. it providesfor an inward radial compone'nt of force on the-anti-extrusion ring 39to force it into sealing engagement with the washpipe 28; 2. it preventsthe anti-extrusion ring 39 from seizing to the sleeve 29; and 3. itprovides lubrication at the sliding surface between the ring 39 andwashpipe 28 or between the ring 39 and end wall 34.

When the washpipe assembly 13 is connected to the swivel and the systemis pressurized, hydraulic force is exerted on the packing. At highpressures, the plastic ring 38 grossly deforms acting much in the mannerof a viscous fluid. It should be noted that the compressive strength ofpolytetrafluoroethylene is only 1,700 psi which is substantially lessthan the pressure imposed on the packing under high pressure drillingconditions. As mentioned above, the hydraulic force transmitted throughthe plastic ring 38 imposes a radial component of force on theanti-extrusion ring 39. This force causes the anti-extrusion ring 39 toyield inwardly conforming to the configuration of the washpipe surfaceand automatically compensates for wear on the anti-extrusion ring 39.The backing provided by the skirt portion of.

the plastic ring 38 prevents the ring 39 from wedging between thewashpipe 28 and sleeve 29. The wear pattern on rings tested indicatedthat the anti-extrusion ring 39 at times remained stationary with thesleeve 29 and at other times rotated with the washpipe 28. In eithersituation, however, the plastic material metering between rubbingsurfaces provides lubrication therefor.

The following test illustrates the effectiveness of the presentinvention. A washpipe assembly similar to that shown in FIG. 2 wasattached to a conventional swivel. The washpipe had an outside diameterof 2.500 inches and each mounting sleeve had an inside diameter of 3.500inches. The packing in each sleeve included a phosphor bronze (SAE 660)anti-extrusion ring 2.504 inches in inside diameter, 3.250 inches inoutside diameter, and 0.250 inches in height. A polytetrafluoroethylenering 3.499 inches in outside diameter, 2.501 inches in inside diameter,and 0.625 inches in height was counterbored to provide a recess havingan inside diameter of 3.250 inches and an axial dimension of 0.250inches. The anti-extrusion ring was inserted into the recess and thisassembly was then inserted into the mounting sleeve. F our self-sealingW elastomer rings were then placed in the sleeve. In the assemblytested, the upper packing provided a dynamic seal between the stationarysleeve and the rotating washpipe whereas the lower packing provided astatic seal between the corotating sleeve and washpipe.

Water was circulated through the swivel at pressures ranging between10,000 and 15,200 psi while the swivel stem was rotated at about 150rpm. The test was conducted for 41.5 hours with only a slight amount ofleakage noted near the end of the test. Following the test, the rings ofthe upper packing were removed for inspection. The metal anti-extrusionring was worn along the surface engaging the end wall of the sleeve andalong its interior surface. This indicates that the anti-extrusion ring39 rotated part of the time with the washpipe and remained stationarypart of the time with the sleeve. The plastic ring extruded inwardlybetween the end wall of the sleeve and the confronting surface of theanti-extrusion ring providing lubrication at the sliding surface. Therewas also evidence that the plastic material provided lubrication betweenthe interior of the anti-extrusion ring and the washpipe.

The above test demonstrates that a swivel provided with the washpipeassembly of the present invention can be used successfully in highpressure drilling operations.

1 claim:

1. An assembly for use in a swivel having two relatively rotatable,fluid conducting members, said assembly comprising a sleeve adapted tobe secured to one of said members, said sleeve including an inwardlyextending end wall having an opening formed therein;

a tube extending through said opening and having an end portion disposedin said sleeve and therewith defining an annular space, said tube andsaid sleeve being relatively rotatable;

means for connecting said tube to the other of said members;

a resin ring having an internal axially extending recess formed therein;7

a circumferentially continuous anti-extrusion ring of a soft bearingmetal having a Brinnel hardness less than about positioned in saidrecess and substantially filling said recess, said resin ring having askirt portion which substantially surrounds the outer periphery of saidanti-extrusion ring, and said resin ring and said anti-extrusion ringbeing positioned in said sleeve wherein said resin ring engages theinner surface of said sleeve and the outer periphery of said tube underpressurized conditions and wherein said anti-extrusion ring engages saidend wall and the outer periphery of said tube; and

at least one seal ring mounted in said sleeve to substantially seal saidannular space, said seal ring being adapted to act on said resin ring totransmit hydraulic forces thereto.

2. An assembly as defined in claim 1 wherein said resin ring is composedof a fluoroplastic.

3. An assembly as defined in claim 2 wherein said fluoroplastic ispolytetrafluoroethylene.

4. An assembly as defined in claim 1 wherein said bearing metal is acopper alloy.

5. An assembly as defined in claim 1 wherein said bearing metal is abronze alloy.

6. An assembly as defined in claim 1 wherein said recess formed in saidresin ring and said anti-extrusion ring are complementary shaped andwherein said recess is sized in relation to said anti-extrusion ringsuch that a portion of the resin ring substantially covers the outerperiphery of said anti-extrusion ring.

7. An assembly as defined in claim 6 wherein said portion has a radialthickness of at least Ill 6 of an inch.

1. An assembly for use in a swivel having two relatively rotatable,fluid conducting members, said assembly comprising: a sleeve adapted tobe secured to one of said members, said sleeve including an inwardlyextending end wall having an opening formed therein; a tube extendingthrough said opening and having an end portion disposed in said sleeveand therewith defining an annular space, said tube and said sleeve beingrelatively rotatable; means for connecting said tube to the other ofsaid members; a resin ring having an internal axially extending recessformed therein; a circumferentially continuous anti-extrusion ring of asoft bearing metal having a Brinnel hardness less than about 100positioned in said recess and substantially filling said recess, saidresin ring having a skirt portion which substantially surrounds theouter periphery of said antiextrusion ring, and said resin ring and saidanti-extrusion ring being positioned in said sleeve wherein said resinring engages the inner surface of said sleeve and the outer periphery ofsaid tube under pressurized conditions and wherein said anti-extrusionring engages said end wall and the outer periphery of said tube; and atleast one seal ring mounted in said sleeve to substantially seal saidannular space, said seal ring being adapted to act on said resin ring totransmit hydraulic forces thereto.
 2. An assembly as definEd in claim 1wherein said resin ring is composed of a fluoroplastic.
 3. An assemblyas defined in claim 2 wherein said fluoroplastic ispolytetrafluoroethylene.
 4. An assembly as defined in claim 1 whereinsaid bearing metal is a copper alloy.
 5. An assembly as defined in claim1 wherein said bearing metal is a bronze alloy.
 6. An assembly asdefined in claim 1 wherein said recess formed in said resin ring andsaid anti-extrusion ring are complementary shaped and wherein saidrecess is sized in relation to said anti-extrusion ring such that aportion of the resin ring substantially covers the outer periphery ofsaid anti-extrusion ring.
 7. An assembly as defined in claim 6 whereinsaid portion has a radial thickness of at least 1/16 of an inch.